Typical internal combustion engines of this type are highly efficient, which leads to an impairment in the warming up of the engine. Cold engine oil causes a rise in the fuel consumption on account of the increased inner friction of the engine. Numerous methods are exploited, in order to warm up the engine oil more rapidly. A customary approach is the use of a chemical heat accumulator. On account of the low heating performance of an appropriate chemical heat accumulator which lies in the range of 2-3 kW, some minutes are required to transfer the completely available heat to the engine. The time for the transfer of the thermal energy has to be as short as possible, in order to achieve significant advantages in saving fuel directly after a cold start of the engine. Furthermore, a coolant circuit through the engine is necessary, in order to transfer the energy of the heat accumulator to the engine.
DE 33 44 484 A1, DE 29 27 680 A1, and EP 2 103 789 A1 disclose systems for warming up an engine and having a heat accumulator and an additional circuit for a coolant.
DE 10 2005 052 632 A1 discloses an apparatus for warming up an engine with an oil heat accumulator. High temperature oil is stored in the oil heat accumulator during operation of the engine. The oil heat accumulator is highly insulated, with the result that the oil can keep its temperature substantially even over a relatively long time period. In the case of a cold start of the engine, the high temperature oil from the oil heat accumulator is first used to lubricate and heat the engine. However, the use of the oil heat accumulator requires high structural outlay, reducing engine efficiency.
The inventors herein have recognized the issues with the above approach and have developed a system to at least partly address them. According to an embodiment of the disclosure, a lubrication system for an internal combustion engine comprises a lubricant circuit, a radiator for cooling the lubricant, a heat accumulator arranged upstream of the engine for warming up the lubricant, the heat accumulator connected in parallel to the radiator, and a valve for switching over the lubricant circuit between the radiator and the heat accumulator.
According to the disclosure, the heating up takes place directly in the lubricant circuit; no additional coolant circuit is required. Therefore, what is known as a “no flow strategy” can be realized, which makes further scope for saving fuel possible. The lubricant is heated up directly and in a targeted manner, with the result that the engine runs with low friction and therefore with low consumption even after a cold start. The connection in parallel of the radiator and the heat accumulator with the valve for switching over is structurally simple and efficient during operation. The lubrication system according to the disclosure can also be retrofitted in existing engines as a result of the simple construction of the lubrication system and the fact that merely a valve and a heat accumulator are required.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure